Photocatalyst and use thereof for decomposing chemical substance

Abstract

A photocatalyst including a metal oxide semiconductor represented by the formula: In 1−x M x AO 4 wherein M represents a transition metal element, A represents an element belonging to the Group 5 a of the Periodic Table and x is a number greater than 0 but smaller than 1.

1. A photocatalyst comprising a metal oxide semiconductor represented by the following formula (1):
   In 1−x  M x AO 4   (1) 
 
       wherein M represents a transition metal element, A represents an element belonging to the Group 5a of the Periodic Table and x is a number greater than 0 but smaller than 1; and
 a co-catalyst of a metal or a metal oxide supported on said metal oxide semiconductor. 
 
     
     
       2. A photocatalyst as claimed in  claim 1 , wherein M is at least one metal selected from the group consisting of Cr, Mn, Fe, Go, Ni, Cu and Zn and A is at least one metal selected from the group consisting of Nb, Ta and V. 
     
     
       3. A photocatalyst as claimed in  claim 1 , wherein said metal oxide semiconductor is represented by the following formula (2) or (3):
   In 1−x Ni x TaO 4   (2) 
   In 1−x Ni x NbO 4   (3) 
 
       wherein x is a number greater than 0 but smaller than 0.5. 
     
     
       4. A photocatalyst as claimed in  claim 1 , wherein said metal oxide semiconductor has a wolframite crystal structure. 
     
     
       5. A photocatalyst as claimed in  claim 1 , wherein said metal oxide semiconductor has visible light activity. 
     
     
       6. A photocatalyst as claimed in  claim 1 , wherein said co-catalyst is selected from Pt, Rh, Ni, nickel oxide, ruthenium oxide and iridium oxide. 
     
     
       7. A method of decomposing a chemical substance, comprising irradiating the chemical substance with light in the presence of a photocatalyst according to  claim 1 . 
     
     
       8. A method as claimed in  claim 7 , wherein the chemical substance is water and wherein the water is decomposed to produce hydrogen and oxygen. 
     
     
       9. A method as claimed in  claim 7 , wherein the chemical substance is a hydrogen-containing material and wherein the hydrogen-containing material is decomposed to produce hydrogen. 
     
     
       10. A method as claimed in  claim 7 , wherein the chemical substance is a harmful material and wherein the harmful material is decomposed into a harmless substance.